Analysis of oils

Importance of the Topic

The precise determination of elemental content in lubricating oils is critical for quality control, regulatory compliance and formulation optimization. X-ray fluorescence (XRF) provides a rapid, non-destructive approach to quantify both trace and major elements in oil matrices without extensive sample preparation.

Objectives and Study Overview

This application note (41701) demonstrates the capability of the Thermo Scientific ARL OPTIM’X WDXRF spectrometer to analyze a variety of elements in oil samples. The aim is to evaluate limits of detection (LODs), precision and ease of use for routine oil analysis in industrial and laboratory environments.

Methodology and Instrumentation

The ARL OPTIM’X is a wavelength-dispersive XRF instrument featuring a low-power Rh anode tube, SmartGonio™ multi-channel optics and optional He/vacuum switching for liquid analysis. Key features include:

• No external/internal water cooling required
• Elemental range from F (Z=9) to U (Z=92), excluding Rh tube interferences
• Up to eight fixed channels for simultaneous measurement or rapid throughput
• User-friendly OXSAS software for instrument control and data processing

Sample preparation is minimal: oils are poured into sealed liquid cells with 4 µm polypropylene film and analyzed directly at 50 W tube power.

Main Results and Discussion

Detection limits and precision were assessed with a 120 s counting time per element. Highlights include:

• LODs in the parts-per-million range (e.g., S ~1.7 ppm, Al ~4.2 ppm, Mg ~8 ppm)
• Reproducibility tests (seven independent cells) for sulfur yielded an average concentration of 25.9 ppm with a standard deviation of 0.6 ppm
• Lead determination showed an average of 4.7 ppm with a 0.6 ppm standard deviation

These results confirm the instrument’s high sensitivity and stability under low-power operation.

Benefits and Practical Applications

The ARL OPTIM’X WDXRF method offers:

• Direct analysis of undiluted oil samples
• Rapid throughput with short measurement times
• High precision and long-term stability for routine monitoring
• Cost-effective operation with minimal maintenance
• Broad element coverage relevant to lubricant formulation and contamination tracking

Future Trends and Applications

Advancements in XRF instrumentation and software are expected to further lower detection limits, enable real-time process monitoring and integrate chemometric tools for multi-element correlation. The technique may expand into new areas such as bio-based lubricants, contamination mapping in used oils and portable field analyzers.

Conclusion

The Thermo Scientific ARL OPTIM’X WDXRF spectrometer delivers ppm-level detection, excellent precision and user convenience for oil analysis, making it a valuable tool for industrial quality assurance and research laboratories.

Reference

Thermo Fisher Scientific, Application Note 41701, 2023.